Album: 2 stroke power assemblies at Iowa City.

Here are a couple EMD 645 power assemblies. The rusty silver cans sitting on top are pistons; two cylinder heads are laying on the ground on each side, with 4 exhaust valves per head. Visible on the cylinder liners is the row of air inlet ports; when the piston reaches the lower end of its stroke these ports are uncovered while simultaneouly the exhaust valves open. Pressurized air from the blower/turbocharger then rushes into the cylinder through these ports, giving a fresh charge of air while also pushing the exhaust gases out through the valves. As the piston comes back up it covers the ports again, the exhaust valves shut, and the air is then compressed by the piston. At or near top dead center the injector (not visible, but it goes in the middle of the head) will inject a measured amount of fuel, and the heat from compression will ignite the fuel, beginning the power stroke.
By: Andy Brown

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